There's a thought.Maybe obsidian never got around to finishing vault 21 and had to come up with a semi plausible explanation for why you cant explore the whole thing.
"Divide and conquer" is the usual translation.I think the expression is universal, but i don't know how you say it in english. Is it "Divide to better reign" or "divide and rule".
Yeah, you have another good point, although it seems to me that if they weren't willing to rebel over their home being destroyed, what would it take? But I think you're right. Like Yamu said, they had little to offer him, not enough to justify the risk they posed, however small it may be.